The role of diagnosticians in terrestrial animal disease surveillance CAHLN presentation, May 2013

Transcription

1 The role of diagnosticians in terrestrial animal disease surveillance CAHLN presentation, May 2013 Julie Paré, DMV, MPVM, PhD Christine Power, DVM MSc Epidemiology and Surveillance Section Animal Health Science Division

2 Surveillance is Ongoing, Systematic Collection Collation Analysis Interpretation of Animal Health Data And Dissemination of Results for Decision Making 2012 OIE Terrestrial Animal Health Code 2

3 Why do we do surveillance in CFIA? To establish Canada s freedom from key terrestrial animal diseases To ensure effectiveness of disease control programs To facilitate export market access NAI 3

4 Meat and Poultry Trade Interprovincial and International + $23.1 B $4.4 B Live Animal Trade Unrestricted Interprovincial Movement International Sales $1.7 B 4

5 How do we do surveillance in CFIA? Collaborative framework Provide leadership - coordination Plan Design Implement Analyse Interpret Report Collaborative Operations Science (Labs) Programs Industry /Pract vets Communication products Peer review publications Comprehensive reports Plan & Design Implement Action Report Analyse & Interpret 5

6 Laboratories involved in every part of surveillance Troubleshooting Testing Test performanc e Implement Disease investigation Test availability Diagnostic testing scheme Plan & Design Consultation Analyse & Interpret Result interpretation Critical review Case definition Report Editing Authorship 6

7 Testing: A critical element of surveillance Surveillance involves the detection of disease or infection according to appropriate case definitions and based on the results of one or more tests for evidence of infection or immune status OIE Terrestrial Animal Health Code. Chapter 1.4 7

8 Case definition The cornerstone Must be defined before first surveillance sample is collected Need for a clear case definition for: Disease response Interpretation of surveillance results OIE reporting Need for inter-branch Communication / Collaboration The case definition Programs How to achieve it Science and Ops 8

9 Case definition for brucellosis A Brucellosis suspect is any animal which has Brucellosis in the differential diagnoses or tests positive to OIE approved and CFIA validated screening and ancillary tests for that species. A Brucellosis positive animal is an animal in which the CFIA confirms the diagnosis of Brucella sp. by growth of the organism in culture with definitive identification by CFIA approved methods. 9

10 Use of case definition in disease control response FPA ielisa Clear test interpretation Negative Seroreactor Negative Seroreactor Brucellosis suspect Clear program response Trace sero-reactor to herd of origin; Apply movement controls; Conduct epi-investigation & herd testing; Order any suspect(s) slaughtered; Culture tissues for B. suis B. suis not isolated Farm is not declared infected B. suis isolated Farm is declared infected Depopulate all exposed susceptible species on infected farm 10

11 Surveillance Evolution - From periodical surveys to ongoing surveillance Collaborative structure Incorporates various sources of surveillance data: Passive surveillance Clinical surveillance Serological surveillance Detection of infectious agent Efficient Ongoing surveillance Probability of freedom 11

12 Scenario tree (freedom) model concepts Probability of Freedom Weight Time Number of animals sampled Accuracy of the test Biosecurity 0 100% Evidence Supporting Freedom Recent testing activity involving many animals Recent testing activities involving few animals Historical testing activities Illustration by R. Vanderstichel, AVC of concept by A. Cameron, AusVet 12

13 Scenario Tree modelling Probability of freedom Allows use of multiple sources of data, each weighted according to it s surveillance value Makes use of historical data Efficiency in work already done by lab (export, dis. Ctrl) Parameter input validity of estimates Sensitivity, specificity of tests Probability of introduction of disease (RA) Risk factors Output: Sensitivity of the surveillance system (SSSe) Probability of freedom OIE supported, international recognition through publications 13

14 Surveillance system Se (SSSe) Probability of freedom Disease detected by SS Disease nondetected by SS Disease Present* Disease absent A B PVP C D PVN SSSe SSSp * At level p 14

15 Probability Output for scenario tree model Surveillance system sensitivity (SSSe) and probability of freedom SSSe P(free) P(intro) Time Period 15

16 We never know what challenges lie ahead: Anaplasma in bovine serological survey BSS Epidemiological analysis of data suggested difference in Anaplasma reactors in BC Within affected herds Mb BC Apparent seroprevalence 6.28% 0.27% Proportion PCR+/ELISA % 4.39% 16

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